Elevator load bearing member having a jacket with at least one rough exterior surface

ABSTRACT

An illustrative method of making a load bearing member for use in an elevator system includes mechanically roughening at least one surface on an exterior of a jacket of the load bearing member to establish a friction characteristic that facilitates engagement between an elevator system sheave and the roughened surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/588,806, which was filed on Sep. 16, 2008, which issued as U.S. Pat.No. 8,449,349, on May 28, 2013.

BACKGROUND

This invention generally relates to load bearing members for use inelevator systems. More particularly, this invention relates to anelevator load bearing member having a specialized jacket surface.

Elevator systems typically include a cab and counterweight that movewithin a hoistway to transport passengers or cargo to different landingswithin a building, for example. A load bearing member, such as roping ora belt typically moves over a set of sheaves and supports the load ofthe cab and counterweight. There are a variety of types of load bearingmembers used in elevator systems.

One type of load bearing member is a coated steel belt. Typicalarrangements include a plurality of steel cords extending along thelength of the assembly. A jacket is applied over the cords and forms anexterior of the assembly. Some jacket application processes result ingrooves being formed in the jacket surface on at least one side of theassembly. Some processes also tend to cause distortions orirregularities in the position of the steel cords relative to theexterior of the jacket along the length of the assembly.

In the case of some coated steel load bearing members, an extrusionprocess for applying a jacket over the cords requires selecting aurethane material having chemical properties that are beneficial for theprocess of applying the jacket. The resulting jacket, however, maypresent difficulties in having the desired level of traction wheninstalled in an elevator system. With some urethane materials that arebeneficial from a processing standpoint, the resulting coefficient offriction between the jacket and an elevator sheave surface may be higheror lower than desirable for meeting the traction requirements within thehoistway.

Typical processes result in a smooth or glossy exterior of the jacket onthe sheave contacting surfaces. In some instances, this smoothness canintroduce undesirable adhesion between the jacket and a traction sheave.In most cases, the resulting coefficient of friction between the smoothsurface and a traction sheave is not consistent with desired tractionperformance.

An alternative arrangement is required to minimize or eliminate theundesirable friction characteristics of a urethane jacket. Thisinvention addresses that need.

SUMMARY

An illustrative method of making a load bearing member for use in anelevator system includes mechanically roughening at least one surface onan exterior of a jacket of the load bearing member to establish afriction characteristic that facilitates engagement between an elevatorsystem sheave and the roughened surface.

According to one example, the jacket is formed to have a generallyrectangular cross-section including a width and a thickness. After thejacket is formed, a device is used to mechanically roughen a generallyplanar surface on one side of the jacket so that the surface is roughacross the entire width.

The various features and advantages of disclosed embodiments will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiments. The drawings thataccompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a portion of an example load beingmember designed according to one embodiment of this invention.

FIG. 2 schematically illustrates a portion of another example loadbearing member designed according to another embodiment of thisinvention.

FIG. 3 is a cross-sectional illustration taken along the lines 3-3 inFIG. 2.

FIG. 4 is a schematic illustration of an example method of making a loadbearing member designed according to an embodiment of this invention.

FIG. 5 schematically illustrates an example tool for performing anotherexample method.

FIG. 6 schematically illustrates one example device used in anembodiment as shown in FIG. 4.

FIG. 7 schematically illustrates another example device used in anembodiment as shown in FIG. 4.

FIG. 8 schematically illustrates another example device used in anembodiment as shown in FIG. 4.

FIG. 9 schematically illustrates another example device used in anotherexample embodiment as shown in FIG. 4.

FIG. 10 schematically illustrates another example device used in anotherexample embodiment as shown in FIG. 4.

FIG. 11 schematically illustrates another example device used in anotherexample embodiment similar to that shown in FIG. 4.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a load bearing member 40 that isdesigned for use in an elevator system. A plurality of cords 42 arealigned generally parallel to a longitudinal axis of the load bearingmember 40. In one example, the cords 42 are made of strands of steelwire.

A jacket 44 generally surrounds the cords 42. In one example, the jacket44 comprises a polyurethane-based material. A variety of polymermaterials are commercially available and known in the art to be usefulfor elevator systems. In one example, the preferred urethane material isa thermoplastic polyurethane (TPU). Given this description, thoseskilled in the art will be able to select a proper jacket material tosuit the needs of their particular situation.

The example jacket 44 establishes an exterior length, L, width, W, and athickness, t, of the load bearing member 40. In one example, the width Wof the load bearing member is approximately 30 millimeters and thethickness t is about 3 millimeters. In the same example, the cords 42have a diameter of 1.65 millimeters. The cords 42 preferably extendalong the entire length L of the assembly. In another example, the loadbearing member is round, rather than rectangular.

The jacket 44 has exterior surfaces 46 and 48. At least one of thesurfaces 46 or 48 will contact a traction sheave and possibly othercomponents within the elevator system as the load bearing member 40moves to provide the desired elevator cab movement. At least theexterior surface 46 is rough across the width W and along the length Lof the example load bearing member 40.

The example assembly includes a plurality of spaced grooves 47periodically interrupting the surface 46, which result from somebelt-making techniques. The portions of the cords at the groovelocations may be at least partially exposed and not fully covered withthe material of the jacket 44 as known. Even though the grooves 47interrupt the surface 46, they are not considered to contribute to or toconstitute the roughness of the surface 46.

The roughness of the example surface 46 includes a plurality of surfaceirregularities that make the surface 46 rough (i.e., not smooth). In theillustrated example, a plurality of impressions 49 are disbursed aboutthe surface 46. In some examples, the pattern of the surfaceirregularities may be established in a controlled manner. In otherexamples, the surface irregularities are randomly disbursed across thesurface 46.

In one example, a plurality of impressions 49 are provided on thesurface 46 that are on the order of at least two microns deep. Inanother example, impressions of about 5 microns deep are included.Deeper impressions or other surface interruptions could be used. Thoseskilled in the art who have the benefit of this description will be ableto select an appropriate depth and pattern, depending on the needs of aparticular embodiment. The impressions in an ester based TPU may be moreshallow than those in an ether based TPU jacket with similar results,for example.

One example includes a surface 46 that has a texture that generallycorresponds to a surface texture on a sheave in the elevator systemwhere the load bearing member is employed. Having a jacket roughnessthat generally corresponds to a sheave roughness includes a roughness onthe jacket surface that is in a general range between about 1/10^(th)the roughness of the sheave and about 10 times the roughness of thesheave. By selecting the roughness of the sheave surface and the jacket,a combination of the surface textures ensures the desired tractionperformance.

FIGS. 2 and 3 show another example embodiment of a load bearing member40′ that is configured as a flat belt but does not include any grooves47 on the surface 46′. In this example, a plurality of impressions 49′are provided on the surface 46′ so that the surface is rough. Theexample of FIGS. 2 and 3 is made using a different manufacturingtechnique than that used to make the example embodiment of FIG. 1 sothat the grooves 47 are only present in the embodiment of FIG. 1.

The rough surface 46, 46′ provides a significantly different coefficientof friction between the load bearing member and a traction sheavecompared to a smooth or glossy surface. The rough surface 46 in someexamples significantly decreases the traction. Depending on the urethanematerial selected for making the jacket 44, 44′, if the coefficient offriction decreases with increased pressure, the rough surface 46effectively increases pressure and decreases friction. On the otherhand, with some urethane materials, the coefficient of frictionincreases with increased pressure so that increased roughness may havethe effect of increasing friction. In either situation, the roughness ofthe surface 46, 46′ significantly decreases adhesion and, therefore,apparent friction. Those skilled in the art who have the benefit of thisdescription will be able to select an appropriate surface texture (i.e.,roughness) to meet the needs of their particular situation taking intoaccount the material selected for making the load bearing memberassembly.

FIG. 4 schematically illustrates a method of making a load bearingmember 40. A cord supply 50 provides the cords 42. A positioning device52 aligns the cords 42 in a desired alignment so that the cords willextend parallel to a longitudinal axis of the load bearing member 40. Atensioning device 54 controls an amount of tension on the cords 42during the jacket application process. The jacket application station 56preferably includes a suitable mold or other device for applying thejacket material onto the cords 42. A supply 58 provides the chosenpolymer material (PU in the illustrated example) to the jacketapplication station 56 in a conventional manner. The jacket material maybe pressure molded, extruded or otherwise applied to the cords 42. Theformed assembly preferably is then processed at a surface finishingstation 60. In the illustrated example, the surface finishing station 60includes at least one device that is used to roughen the surface 46 ofthe jacket 44. The processing at the finishing station 60 may be dry orwet, depending on desired material handling, for example.

Further details regarding one example consistent with FIG. 4 can befound in the published application WO 2003/042085. The teachings of thatdocument are incorporated into this description by reference.

FIG. 6 schematically illustrates one device for roughening the surface46. A roller 63 includes a surface pattern 64 that embosses the surface46 with a desired amount of roughness. In one example, the formed loadbearing member passes between the roller 63 and another roller (notillustrated) having a smooth surface so that only one side of the jacket44 has a roughened surface 46. In another example, opposing rollers 63engage both sides of the jacket 44 so that the surfaces 46 and 48 areroughened. In one example, the roller 63 is freewheeling and movesresponsive to movement of the load bearing member as it passes by theroller. In another example, the roller is motorized so that it moves ata controlled rate. A variety of embossing patterns may be used toestablish the desired surface texture on the roughened surface. Thoseskilled in the art who have the benefit of this description will be ableto select appropriate arrangements to meet the needs of their particularsituation.

FIG. 7 schematically illustrates another device that is used in anembodiment of this invention for roughening the surface 46 of the jacket44. In the example of FIG. 7, an abrading pad 65 has a rough surface 66that is supported in machinery of the finishing station 66 so that thesurface 66 engages at least the surface 46 of the jacket 44. In oneexample, moving machinery causes the abrading device 65 to move rapidlyin a circular or reciprocal motion to rub against the jacket 44 forroughening the surface 46.

FIG. 8 schematically illustrates another example where an abrasive sheet67 such as sandpaper is appropriately supported within the finishingstation 60 so that it contacts at least the surface 46 for rougheningthe surface a desired amount.

FIG. 9 schematically illustrates another device for roughening thesurface 46. In this example, a buffing pad 68 is supported in anappropriate manner to rub against at least the surface 46 to buff thesurface until it has an appropriate amount of roughness.

The particular device or devices shown for roughening the surface 46 mayvary depending on the particular material selected for making the jacketand the particular surface texture desired for a given application.Those skilled in the art who have the benefit of this description willrealize what will work best for their situation, which may include acombination of more than one of the devices described here or other,similarly functional devices.

While the examples of FIGS. 6-9 illustrate mechanical rougheningtechniques, another example finishing station 60 utilizes a chemicalroughening process. FIG. 10 schematically shows an applicator 69 that isuseful for applying a chemical to the surface 46 to achieve a desiredroughness. Applying a chemical wash to at least the surface 46 is usedin one example to partially erode the material on the surface 46resulting in a roughened surface once the chemical wash is rinsed away,by water for example. In another example, a chemical etching techniqueis applied to at least the surface 46. Those skilled in the art who havethe benefit of this description will be able to select appropriatechemicals and processing times to achieve the desired roughness of atleast the surface 46 to meet the needs of their particular situation.

In one example, the finishing station 60 also includes a forming device,a dimensional inspection device and a curing cold water bath where thejacket material and the cords within the material are cooled to asuitable temperature. The finishing station forming device preferablyincludes a rigid structure that forces the jacket to have a desiredexterior configuration (i.e., a rectangular cross section). Theinspection device, such as a known laser triangulation measuring device,determines whether the desired geometry was achieved.

The resulting load bearing member 40 preferably is then stored at 62,for example on spools for shipment to various locations for installationin elevator systems. The load bearing member 40 may be precut tospecific lengths or may be provided in larger quantities where atechnician at the installation selects the appropriate amount of beltmaterial for a particular application.

FIG. 5 schematically illustrates an example molding device 70 forapplying the jacket 44 to the cords 42 and roughening at least onesurface of the jacket 44. The example of FIG. 5 may be used in anarrangement as schematically shown in FIG. 4. When the techniquesassociated with the example of FIG. 5 are used, the finishing station 60may not require any device for roughening the surface 46. As will bedescribed, the surface roughness can be established during the extrusionprocess where the jacket 44 is applied to the cords 42. Additionalroughness may be accomplished using a roughening device within thefinishing station 60 even where a technique as schematically shown inFIG. 5 is employed.

The example forming device 70 of FIG. 5 includes a mold housing 72having an input side 74. A cord positioning device 76 preferably issituated at the input side 74. The cord positioning device 76 includes aplurality of openings 78 through which the cords 42 are fed into thedevice 70. The openings 78 preferably are accurately machined orotherwise formed so that a close tolerance is kept between the exteriorof the cords 42 and the interior of the openings 78. Having a tight fitbetween the openings 78 and the cords 42 prevents backflow of the jacketmaterial during the molding process.

The mold housing 72 includes one or more openings 79 through which thejacket material is applied to the cords using pressure injection. Asknown in the art, pressure injection can be used for molding materialssuch as polyurethane when the material is suitably heated. Given thisdescription, those skilled in the art will be able to select appropriateconditions for achieving a desired result.

The molding device 70 includes a temperature controlled opening 80 at anoutput side 82 of the mold housing 72. The opening 80 preferably isshaped to control the exterior shape and surfaces on the load bearingmember 40. Moreover, the opening 80 is temperature controlled forachieving a desired effect on the exterior of the jacket 44. In oneexample, the temperature within the mold housing 72 is higher than thetemperature of the opening 80. By having a reduced temperature near theexit of the mold 72, so-called melt fracture occurs. During meltfracture in this example, the surface 46 of the jacket 44 becomesroughened.

Reducing the temperature of the opening 80 relative to the temperaturein the mold housing 72 effectively cools the surfaces of the jacket 44as the assembly exits the mold housing 72. During such cooling, aportion of the jacket material is effectively solidified against thewall of the opening 80 and then torn away as the assembly continuesthrough the mold machinery. This effect induces or creates turbulencewithin the jacket material and prevents the components within thepolyurethane stock material that are not pure polyurethane fromcompletely migrating to the surface 46 of the jacket 44. It is knownthat during formation of most polyurethane materials, an amide richlayer forms on an exterior. The various additives to a polyurethanematerial including waxes, mold release agents, etc., typically migrateto the exterior surface and form a thin layer, which may be less than0.1 millimeter, containing “impurities” added to the stock ofpolyurethane. Inducing melt fracture (by lowering the temperature of theopening 80 relative to the rest of the mold, for example) allows thetypical amide-rich layer to only partially form and results in anirregular surface 46 that has a roughness sufficient for accomplishingthe objectives of an embodiment of this invention. Themicro-irregularities in the surface 46 caused by melt fracture mayinclude impressions 49 on the order of five microns, which is sufficientto enhance the friction characteristics of the jacket 44 for somepolyurethane materials.

In another example, localized heating of the surface 46 is used toroughen the surface 46 by causing localized vaporizing, melting orburning of the surface material of the jacket 44. FIG. 11 schematicallyshows a precise heat source 90 that heats at least selected portions ofthe surface 46 to cause the desired localized change in the surface. Inone example, the heat source 90 directs a laser beam 92 at the jacketsurface. In another example, the heat source 90 directs an electron beam92 at the jacket surface.

According to one embodiment, the heat source 90 is positioned within orbefore the finishing station 60 of FIG. 4. Using localized heating maybe most advantageously used before the jacket material is cooled in awater bath, for example. Given this description, those skilled in theart will be able to select an appropriate arrangement and appropriateparameters to meet the needs of their particular situation.

Whether roughening the surface 46 during jacket formation or after thepolyurethane is at least partially cooled, the resulting non-smooth,non-glossy surface provides enhanced traction control. The disclosedtechniques can be used to provide a variety of surface textures.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this invention. The scope of legal protection given tothis invention can only be determined by studying the following claims.

We claim:
 1. A method of making a load bearing member for use in anelevator system, comprising: generally surrounding at least one tensionmember with a polymer jacket having a generally rectangularcross-section including a width and thickness, at least one of twooppositely facing sides of the jacket being configured to contact asheave in an elevator system, the width extending across the sides ofthe jacket, respectively; forming the jacket; moving an abrading deviceinto engagement with the surface; and mechanically roughening a surfaceof at least one of the two sides to establish a friction characteristicthat facilitates engagement between an elevator system sheave and theroughened surface by causing relative movement between the abradingdevice and the surface sufficiently to achieve a selected roughness onthe surface.
 2. The method of claim 1, wherein mechanically rougheningincludes abrading the surface.
 3. The method of claim 1, whereinmechanically roughening includes rubbing the surface.
 4. The method ofclaim 1, wherein mechanically roughening includes grinding the surface.5. The method of claim 1, wherein mechanically roughening includesembossing the surface to establish a plurality of impressions across thewidth of the surface.
 6. The method of claim 1, including establishing aplurality of impressions on the surface having a depth of at leastapproximately 5 microns.
 7. The method of claim 6, wherein the pluralityof impressions are randomly distributed across the width and along alength of the surface.
 8. The method of claim 1, including establishinga non-glossy texture on the surface.
 9. The method of claim 1,comprising mechanically roughening only one of the two oppositely facingsides; and leaving the other of the two oppositely facing sidesgenerally smooth.
 10. The method of claim 1, comprising moving theabrading device in a generally circular pattern.
 11. The method of claim1, comprising moving the abrading device in a reciprocal manner.
 12. Themethod of claim 1, comprising roughening the surface across the entirewidth.
 13. A method of making a load bearing member for use in anelevator system, comprising: generally surrounding at least one tensionmember with a polymet jacket having a generally rectangularcross-section including a width and thickness, at least one of twooppositely facing sides of the jacket being configured to contact asheave in an elevator system, the width extending across the sides ofthe jacket, respectively; forming the jacket; passing the formed jacketby at least one roller positioned to engage the surface; andmechanically roughening a surface of at least one of the two sides toestablish a friction characteristic that facilitates engagement betweenan elevator system sheave and the roughened surface by moving the rollerin a manner that roughens the surface.
 14. The method of claim 13,comprising moving the formed jacket between two opposing rollerssituated to engage the two oppositely facing sides of the jacket,wherein at least one of the rollers has a roller surface configured toroughen the surface of the jacket.
 15. The method of claim 14, whereinboth of the two rollers have a roller surface configured to roughen thesurface on a corresponding side of the jacket so that the surface oneach of the two oppositely facing sides are roughened as the jacketmoves between the rollers.